Impulse generating system



April 29, 1947. G. J. LEHMANN 2,419,574

IMPULSE GENERATING SYSTEM Filed OC. 50, 1945 2 SheetS-Sheet 2 -HIIIHH Aas J9 Mfg-*w* W53 i HIHHI SCM 51 ATOR d Bumm J9 I l J2 Il -HHHHI *wh- IWJ3 -lmllm J5 Mrd L /I TTOHNEY Patented Apr. 29, 1947 IMPULSE GENERATINGSYSTEM Gerard J. Lehmann, New York, N. Y., assignor to InternationalStandard Electric Corporation, New York, N. Y., a corporation ofDelaware f vApplication October 30, 1943, Serial No. 508,288

4 Claims.

This invention relates to impulse generating systems and especially toapparatus of this type which includes an arrangement capable ofgenerating pulses having very high instantaneous power values, used forplate modulation oi an oscillator, which may be of a type that hasrecently come into widespread use for certain special purposes.

An object of the invention is to provide a system including a high powerpulse generator that does not require the use of generating tubes.'I'his .is in general accomplished by utilizing a plurality of spark gapunitsv including condensers which are charged in parallel and dischargedin series. Afeature of this arrangement is the production of pulseshaving high voltage and power values from sources having relatively lowvaines.

Av further feature is the provision of a modulation system including aspark gap and condenser arrangement adapted to produce discharges at arate that is in the desired audible frequency range. Other featuresinclude uniformity and ready regulation of pulse frequency, and thedevelopment of voltage and power substantially beyond maximumrequirements.

Other objects and advantages will appear from the following descriptionconsidered in connection with the accompanying drawings, in which Fig. lis a diagram of a system embodying the invention, and

Fig. 2 is a diagram of a modification of said system.

The arrangement disclosed in Fig. 1 includes a plurality of spark gapsI0 of the quenched type, connected in series with a condenser Ipreceding each gap. Each condenser is connected across charging lines|2, I3 through resistors 4. Line I2 is grounded, and I3 is connected atB to the positive side of a direct current charging source I5, thenegative side of which is also grounded. With this arrangement thecondensers H are charged in parallel through resistors I4 from sourceI5, Whose potential is relatively high but insuicient to initiate adischarge through the spark gaps I0.

Means is provided for applying to the first condenser a triggering pulsehaving the proper potential for initiating a discharge through thesucceeding spark gap I0. This is conveniently accomplished by utilizinga tube I8 having its cathode I9 connected to line I2 and its anode 29connected through condenser 2| to the positive side of the rst condenserII, said anode being connected through a suitable resistor 22 to thepositive side of source I5. The grid 23 receives triggering impulses atsuitable frequency from a pulse generator 24; and one advantage of thedisclosed arrangement is the fact that said pulse generator may be ofrelatively low power.

When a pulse from generator 24 is supplied to grid 23 the correspondingpulse from anode 20 is applied to the first condenser II, at a Voltagesuilicient to discharge the condenser through the succeeding spark gapIii. The other condensers I I are discharged in sequence through theassociated spark gaps, providing a cascade pulse of high power andpotential. The duration of the discharge is so short that the resistorsN are adequate to prevent any material interaction with the lines i2,I3.

In.order to prevent the current through the condensers and spark gapsfrom passing through the lowermcst resistor I4 to line I2 and ground, abypass spark gap 26 is connected between the negative side of the firstcondenser I I and line I2. The bypass gap does not pass the chargingcurrent to the adjacent condenser but provides a low resistance path forthe current when the condensers I I are discharging. With thisarrangement the value of condenser 2| may be relatively low, and that ofresistor 22 relatively high, tube I8 operating at high impedance and lowpower.

Pulses generated in the indicated manner have very steep wave fronts,which are objectionable, particularly for modulation; and a suitablenetwork is provided for attening the front of each pulse wave to thedesired slope. In the form illustrated the network includes groundedcondensers 21 and an intermediate inductor 28 in the output line 29 fromthe last spark gap I0. Line 29 is connected to oscillator 30 so as tomodulate the oscillator output, being shown as connected to theoscillator anode circuit 3| to provide the anode voltage supply, thepulse circuit being completed by the usual oscillator cathode groundconnection 32, the modulated oscillations being transmitted throughoutput transformer 33.

In the arrangement shown in Fig, 1 the charging of condensers isrestricted by the use of the resistors |4. This restriction iseliminated in the arrangement illustrated in Fig. 2, in which thecondensers are charged by an alternating voltage. In this embodiment thecharging voltage is obtained from an alternator 35 through transformer36 having a secondary winding 31 in line I3, the lower end of thesecondary being grounded. The pulse generator 24 is synchronized witha1- ternator 35 in such manner that the condenser discharge willcoincide with the start ofa charging cycle, suitable synchronizing leadconnections 38 being shown. The frequency of the alternator may be thesame as that of the pulse generator or a multiple thereof.

In this arrangement the resistors I4 are replaced by choke coils 39,which are designed to isolate the condensers H during discharge Withoutinterfering materially with the charging of said condensers. Theytherefore may consist of air core inductors having a small number ofturns, offering no material resistance to the charging current. Theoutput inductances of the alternator 35 and of the transformer'SB aredesigned for resonance with the parallel condenser units, therebyobtainingr eicient charging.

With the described arrangements a frequency of 250 pulses per second atexceptionally high voltage and amperage can be obtained, the pulsesbeing of very short duration such as 5 to 7 microseconds. Voltages ashigh as 90,000 volts and an average value of useful power up to twokilowatts have been obtained. The application of pulses of this type tothe modulation of the plate circuit of an oscillator results in thedevelopment of powerful impulses in the oscillator output which are ofgreat value for certain purposes. Moreover, the frequency of suchimpulses is readily controlled and altered, and has a high degree ofuniformity.

What is claimed is:

l. A system for generating electrical pulses as set forth in claim 2comprising a connection between the rst condenser in the series andground, said connection including a spark gap proportioned to preventcurrent ow during charging and to permit current flow during dischargeof thecondensers.

v2. A system for generating regularly repetitive high voltage electricalpulses comprising a plurality of condensers and discharge devicesconnected alternately in series, means for charging the condensers to aVoltage below the breakdown voltage of said discharge devices includinga source of charging energy connected to said condensers in parallel, asource of low voltage electrical triggering pulses, a vacuum tubecomprising a cathode, a control grid and an anode, means for connectingsaid source of low voltage electrical pulses to said grid, and means forconnecting said cathode and anode to the respective terminals of one ofsaid condensers.

3. A system for generating electrical pulses as set forth in claim 2, inwhich said charging source is connected to supply said anode of saidvacuum tube with a high potential.

4. A system for generating electrical pulses as set forth in claim 2 inwhich said charging source comprises a source of alternating currentsynchronized with said rsource of low voltage triggering pulses andcoupledto the 4anode of said vacuum tube.

GERARD J. LEHMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date f 2,276,994 Milinowski Mar. 17.,1942 2,295,585 Lindquist Sept. 15, 1942k 2,032,904 Bellaschi Mar. 3,1936y 2,077,773 Rorden Apr..20, 1937 2,221,573 Bruckmann Nov. 12, 19402,228,070 Belloschi Jan. 7, 1941 2,235,399 Diehl Mar. 18, 1941

